An Organic Light Emitting Diode (OLED) has such unique features that it is self-emissive, fast response, and wide viewing angle, can be made on a flexible substrate, and so on, and display based on OLEDs is becoming the mainstream in the field of display.
An OLED display back panel comprises a TFT substrate, an ITO (Indium Tin Oxide) pixel electrode, a light emitting layer, a cathode, etc. A pixel defining layer is produced on the TFT substrate, and each pixel defining zone of it corresponds to one pixel electrode. The finer and denser each pixel defining zone and a pixel electrode corresponding to each pixel defining zone are, the higher the resolution of products is, but the finely divided pixel defining zone has been limited by printing technology. With the size of a pixel defining zone being 30 μm×90 μm as an example, when diameter of droplets formed by an inkjet head of a printer is equal to 30 μm, it is at the same level as size of a pixel. When an OLED device is fabricated with the ink-jet printer, it is necessary to take control of droplets, so that they precisely fall onto a pixel defining zone, and thickness of a thin film is uniform after the droplets falling into the pixel defining zone have been dried.
In prior art, control of precisely falling onto the pixel defining zone of droplets needs a printing equipment with a high alignment accuracy, and this requires increasing of the investment of equipment, leading to a higher cost. Furthermore, it is hard to form a thin film with a uniform thickness due to the fact that size of the pixel defining zone is smaller and flowability of the liquid is poor, and thus the quality of emission of the display back panel is affected.